U.S. patent application number 15/124231 was filed with the patent office on 2017-02-09 for optoelectronic modules operable to recognize spurious reflections and to compensate for errors caused by spurious reflections.
This patent application is currently assigned to Heptogaon Micro Optics Pte Ltd.. The applicant listed for this patent is HEPTAGON MICRO OPTICS PTE. LTD.. Invention is credited to Stephan Beer, Bernhard Buettgen, Bassam Hallal, Jens Kubacki, Michael Lehmann, Jim Lewis, Daniel Perez Calero, Miguel Bruno Vaello Panos.
Application Number | 20170038459 15/124231 |
Document ID | / |
Family ID | 52785552 |
Filed Date | 2017-02-09 |
United States Patent
Application |
20170038459 |
Kind Code |
A1 |
Kubacki; Jens ; et
al. |
February 9, 2017 |
OPTOELECTRONIC MODULES OPERABLE TO RECOGNIZE SPURIOUS REFLECTIONS
AND TO COMPENSATE FOR ERRORS CAUSED BY SPURIOUS REFLECTIONS
Abstract
Optoelectronic modules (100) are operable to distinguish between
signals indicative of reflections from an object of interest and
signals indicative of a spurious reflection. Various modules are
operable to recognize spurious reflections by means of dedicated
spurious-reflection detection pixels (126) and, in some cases, also
to compensate for errors caused by spurious reflections.
Inventors: |
Kubacki; Jens; (Affoltern am
Albis, CH) ; Lewis; Jim; (Zurich, CH) ; Vaello
Panos; Miguel Bruno; (Zurich, CH) ; Lehmann;
Michael; (Winterthur, CH) ; Beer; Stephan;
(Schaffhausen, CH) ; Buettgen; Bernhard;
(Adliswil, CH) ; Perez Calero; Daniel; (Zurich,
CH) ; Hallal; Bassam; (Thalwil, CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HEPTAGON MICRO OPTICS PTE. LTD. |
Singapore |
|
SG |
|
|
Assignee: |
Heptogaon Micro Optics Pte
Ltd.
Singapore
SG
|
Family ID: |
52785552 |
Appl. No.: |
15/124231 |
Filed: |
March 13, 2015 |
PCT Filed: |
March 13, 2015 |
PCT NO: |
PCT/EP2015/055358 |
371 Date: |
September 7, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61953089 |
Mar 14, 2014 |
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61981235 |
Apr 18, 2014 |
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61987045 |
May 1, 2014 |
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62001858 |
May 22, 2014 |
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62006989 |
Jun 3, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 17/89 20130101;
G01J 1/0204 20130101; G01J 1/0422 20130101; G01J 1/4204 20130101;
G01J 1/0214 20130101; G01S 17/894 20200101; G01S 17/36 20130101;
G01J 1/0407 20130101; G01S 7/4813 20130101; G01S 7/497 20130101;
G01J 1/0425 20130101; G01J 1/0411 20130101; G01S 2007/4975
20130101 |
International
Class: |
G01S 7/497 20060101
G01S007/497; G01S 17/36 20060101 G01S017/36; G01S 17/89 20060101
G01S017/89; G01S 7/481 20060101 G01S007/481 |
Claims
1. An optoelectronic module comprising: a light emitter to generate
light to be emitted from the module; a plurality of spatially
distributed light sensitive elements arranged to detect light from
the emitter that is reflected by an object outside the module; and
one or more dedicated spurious-reflection detection pixels.
2. The optoelectronic module of claim 1 wherein the light emitter
is disposed in a first chamber of the module and the spatially
distributed light sensitive elements and one or more dedicated
spurious-reflection detection pixels are disposed on a second
chamber of the module.
3. The optoelectronic module of claim 1 including circuitry
operable to use a signal from the one or more dedicated
spurious-reflection detection pixels to correct for a spurious
reflection.
4. The optoelectronic module of claim 3 including circuitry
operable to use a signal from the one or more dedicated
spurious-reflection detection pixels to factor out a component of
light reflected by a smudge present on a transmissive cover from a
component of light detected by the spatially distributed light
sensitive elements.
5. The optoelectronic module of claim 1 including circuitry
operable to use output signals from the one or more dedicated
spurious-reflection detection pixels to determine whether a smudge
is present on a glass cover of a host device in which the module is
disposed.
6. The optoelectronic module of claim 1 wherein the spatially
distributed light sensitive elements are demodulation pixels, the
module further including processing circuitry operable to determine
a distance to an object outside the module based at least in part
on signals from the demodulation pixels.
7. The optoelectronic module of claim 1 further including a
reflector to direct a spurious light reflected by a smudge, a
transmissive cover or other component to the one or more dedicated
spurious-reflection detection pixels.
8. The optoelectronic module of claim 7 wherein the module is
disposed within a host device that includes a transmissive cover,
and wherein the reflector is disposed so to direct light reflected
by a smudge on the transmissive cover to the one or more dedicated
spurious-reflection detection pixels.
9. The optoelectronic module of claim 1 further including a light
guide to direct light from a transmissive cover of a host device
within which the module is disposed to the one or more dedicated
spurious-reflection detection pixels.
10. The optoelectronic module of claim 9 wherein the light guide is
disposed to receive light reflected by a smudge on a surface of the
transmissive cover and reflected internally within the transmissive
cover, and to guide the received light to the one or more dedicated
spurious-reflection detection pixels.
11-16. (canceled)
17. An optoelectronic module comprising: a light emission chamber
and a light detection chamber; a first passive optical element
disposed over the light emission chamber and a second passive
optical element disposed over the light detection chamber; a light
emitter in the light emission chamber operable to emit light toward
the first passive optical element; a plurality of demodulation
pixels in the light detection chamber arranged to detect light from
the emitter that is reflected by an object outside the module; one
or more spurious-reflection detection pixels in the light detection
chamber; and one or more light absorbing regions in or on the
second passive optical element arranged to block emitter light
reflected from one or more pre-defined areas of a transmissive
cover of a host device from reaching the demodulation pixels.
18. The optoelectronic module of claim 17 wherein the one or more
light absorbing regions are disposed so as to allow emitter light
reflected by an object outside the module back toward the module to
pass through the second passive optical element to the demodulation
pixels.
19. The optoelectronic module of claim 17 wherein each of the one
or more light absorbing regions comprises a black chrome
coating.
20. The optoelectronic module of claim 17 wherein each of the one
or more light absorbing regions is a laser blackened region of the
second passive optical element.
21. An optoelectronic module comprising: a light emission chamber
and a light detection chamber; a first passive optical element
disposed over the light emission chamber and a second passive
optical element disposed over the light detection chamber; a light
emitter in the light emission chamber operable to emit light toward
the first passive optical element; a plurality of demodulation
pixels in the light detection chamber arranged to detect emitter
light that is reflected by an object outside the module back into
the module; one or more spurious-reflection detection pixels in the
light detection chamber; and one or more light redirecting elements
in or on the second passive optical element arranged to redirect at
least some light impinging on the second passive optical element
toward the one or more spurious-reflection detection pixels and
away from the demodulation pixels.
22. The optoelectronic module of claim 21 wherein each of the light
redirecting elements is a diffractive or refractive element.
23. An optoelectronic module comprising: a light emission chamber
and a light detection chamber; a first passive optical element
disposed over the light emission chamber and a second passive
optical element disposed over the light detection chamber; a light
emitter in the light emission chamber operable to emit light toward
the first passive optical element; a plurality of demodulation
pixels in the light detection chamber arranged to detect emitter
light that is reflected by an object outside the module back into
the module; one or more spurious-reflection detection pixels in the
light detection chamber; and one or more light redirecting elements
in or on the first passive optical element arranged to redirect at
least some emitter light impinging on the first passive optical
element toward a pre-defined area.
24. The optoelectronic module of claim 23 wherein each of the light
redirecting elements is arranged to redirect at least some of the
emitter light toward a particular respective region of a
transmissive cover of a host device in which the module is
disposed.
25. The optoelectronic module of claim 23 wherein each of the light
redirecting elements is a refractive or diffractive element.
26-30. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of the
following U.S. Provisional Patent Applications: Ser. No. 61/953,089
filed on Mar. 14, 2014; Ser. No. 61/981,235 filed on Apr. 18, 2014;
Ser. No. 61/987,045, filed on May 1, 2014; Ser. No. 62/001,858,
filed on May 22, 2014; and Ser. No. 62/006,989, filed on June 3,
2014. The contents of the prior applications are incorporated
herein by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to modules that provide
optical signal detection.
BACKGROUND
[0003] Some handheld computing devices such as smart phones can
provide a variety of different optical functions such as
one-dimensional (1D) or three-dimensional (3D) gesture detection,
3D imaging, time-of-flight or proximity detection, ambient light
sensing, and/or front-facing two-dimensional (2D) camera
imaging.
[0004] Time-of-flight (TOF) sensors, for example, can be used to
detect the distance to an object. In general, TOF systems are based
on the phase-measurement technique of emitted intensity-modulated
light, which is reflected by a scene. The reflected light is imaged
onto a sensor, and the photo-generated electrons are demodulated in
the sensor. Based on the phase information, the distance to a point
in the scene for each pixel is determined by processing circuitry
associated with the sensor.
[0005] Additionally, TOF-based systems can provide depth and/or
distance information via a pulse-measurement technique. The
pulse-measurement technique employs an emitter and sensor as above;
however, distance is determined by tallying the time for emitted
light to reflect back onto the sensor.
[0006] In some cases, however, a smudge (e.g., a fingerprint or
dirt) on the transmissive window (e.g., cover glass) of the host
device can produce spurious signals, which may compromise the
accuracy of the distance calculations. For example, light reflected
by the cover glass and/or the smudge may be incident on the sensor.
Such light typically will have a phase shift that differs from the
phase shift of light reflected by the object of interest. The
different phase shifts can result in an inaccurate determination of
the distance to the object.
SUMMARY
[0007] The present disclosure describes optoelectronic modules
operable to distinguish between signals indicative of reflections
from an object of interest and signals indicative of a spurious
reflection. In particular, as described below, various modules are
operable to recognize spurious reflections and, in some cases, also
to compensate for errors caused by spurious reflections.
[0008] For example, in one aspect, an optoelectronic module
includes a light emitter to generate light to be emitted from the
module, spatially distributed light sensitive elements arranged to
detect light from the emitter that is reflected by an object
outside the module, and one or more dedicated spurious-reflection
detection pixels. In some implementations, the optoelectronic
module further includes circuitry operable to use a signal from the
one or more dedicated spurious-reflection detection pixels to
correct for a spurious reflection. For example, in some cases, the
circuitry can use a signal from the one or more dedicated
spurious-reflection detection pixels to factor out a component of
light reflected by a smudge present on a transmissive cover from a
component of light detected by the spatially distributed light
sensitive elements.
[0009] In some instances, the modules includes a reflector to
direct a spurious light reflected by a smudge, a transmissive cover
or other component to the dedicated spurious-reflection detection
pixels. Likewise, in some cases, the module includes a light guide
to direct light from a transmissive cover of a host device within
which the module is disposed to the dedicated spurious-reflection
detection pixels.
[0010] In accordance with another aspect, an optoelectronic module
includes a light emission chamber and a light detection chamber. A
first passive optical element is disposed over the light emission
chamber, and a second passive optical element is disposed over the
light detection chamber. A light emitter in the light emission
chamber is operable to emit light toward the first passive optical
element. Demodulation pixels in the light detection chamber are
arranged to detect light from the emitter that is reflected by an
object outside the module. Further, one or more spurious-reflection
detection pixels also are in the light detection chamber. One or
more light absorbing regions are provided in or on the second
passive optical element and are substantially non-transparent to
light at a wavelength emitted by the light emitter.
[0011] In some implementations, the light absorbing regions define
a narrow straight path from a predefined area on a surface of a
transmissive cover of a host device to the one or more
spurious-reflection detection pixels. In some instances, the light
absorbing regions are arranged to block emitter light reflected
from one or more pre-defined areas of the transmissive cover from
reaching the demodulation pixels. Further, in some implementations,
there may be one or more light redirecting elements in or on the
second passive optical element arranged to redirect at least some
light impinging on the second passive optical element toward the
spurious-reflection detection pixels and away from the demodulation
pixels. In some cases, there may be one or more light redirecting
elements in or on the first passive optical element arranged to
redirect at least some emitter light impinging on the first passive
optical element toward a pre-defined are.
[0012] In another aspect, an optoelectronic module includes a light
emitter operable to emit light out of the module and demodulation
pixels arranged to detect emitter light that is reflected by an
object outside the module back into the module. The module further
includes one or more combined spurious-reflection
detection-reference pixels, as well as processing circuitry to
correct for spurious reflections and to compensate for thermal
drift based on signals from the one or more combined
spurious-reflection detection-reference pixels. For example, in
some implementations, the processing circuitry is configured to
correct for spurious reflections based at least in part on signals
from the one or more combined spurious-reflection
detection-reference pixels and also is configured to compensate for
thermal drift based at least in part on phase shifts in the signals
from the one or more combined spurious-reflection
detection-reference pixels.
[0013] Another aspect describes a method of operating an
optoelectronic module comprising demodulation pixels. The method
includes emitting light from the module toward an object outside
the module at a first modulation frequency, detecting, in the
demodulation pixels, light reflected from the object at the first
modulation frequency, emitting light from the module toward the
object outside the module at a second modulation frequency and
detecting, in the demodulation pixels, light reflected from the
object at the second modulation frequency. The method further
includes identifying a component in the signals detected by the
demodulation pixels, wherein the component is caused by a
reflection from a smudge on a cover glass, or a reflection from the
cover glass, from a filter, or from another optical or non-optical
element in the optoelectronic module or host device in which the
optoelectronic module is disposed. The method includes subtracting
out the component so as to determine a phase shift and amplitude
resulting from light reflected by the object.
[0014] Other aspects, features and advantages will be readily
apparent from the following detailed description, the accompanying
drawings, and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 illustrates an example of a TOF sensor module.
[0016] FIG. 2 is a flow chart showing a method of compensating for
spurious reflections.
[0017] FIG. 3 is another example of a TOF sensor module.
[0018] FIG. 4 is yet another example of a TOF sensor module.
[0019] FIG. 5 illustrates a further example of a TOF sensor
module.
[0020] FIG. 6 illustrates an example of a TOF sensor module.
[0021] FIG. 7 illustrates another example of a TOF sensor
module.
[0022] FIG. 8 illustrates a further example of a TOF sensor
module.
[0023] FIG. 9 illustrates yet another example of a TOF sensor
module.
[0024] FIG. 10 illustrates a further example of a TOF sensor
module.
[0025] FIG. 11 is an example of a phasor diagram based on TOF
measurements using two different modulation frequencies.
DETAILED DESCRIPTION
[0026] FIG. 1 illustrates an example of an optoelectronic module
100 that includes a light emission channel 102 and a light
detection channel 104. A light emitter 106 (i.e., an illumination
source) and a TOF sensor 108 are mounted on a first side of a
printed circuit board (PCB) 110, which forms the bottom side of the
module housing. The light emitter 106 can be operable to generate
coherent, directional, spectrally defined light emission with
minimal divergence relative to the emission axis (e.g., in the
range of 10 to 20 degrees). Examples of the light emitter 106 are a
laser diode or a vertical cavity surface emitting laser
(VCSEL).
[0027] A spacer 114 is attached to the first side of the PCB 110
and separates the PCB 110 from an optics member 116. The spacer 114
can be composed of a material (e.g., epoxy resin) and have a
thickness such that it is substantially non-transparent to
wavelengths of light detectable by the TOF sensor 108. An interior
wall 115 of the spacer 114 provides optical isolation between the
module's two chambers (i.e., the light emission chamber (channel)
102 and the light detection chamber (channel) 104).
[0028] The optics member 116 includes a respective passive optical
element (e.g., a lens) 120A, 120B for each channel 102, 104. Light
from the emitter 106 is directed out of the module 100 and, if
reflected by an object back toward the module's detection channel
104, can be sensed by the TOF sensor 108.
[0029] The TOF sensor 108 includes an array of spatially
distributed light sensitive elements (e.g., pixels), as well as
logic and other electronics to read and process the pixel signals.
The pixels can be implemented, for example, in a single integrated
semiconductor chip (e.g., a CCD or CMOS sensor). The emitter 106
and the TOF sensor 108 can be connected electrically to the PCB
110, for example, by conductive pads or wire bonds. The PCB 110, in
turn, can be connected electrically to other components within a
host device (e.g., a smart phone). The TOF sensor 108 is operable
to resolve distance based on the known speed of light by measuring
the time-of-flight of a light signal between the sensor and the
subject for each point of an object. The circuitry in the TOF
sensor 108 can use signals from the pixels to calculate, for
example, the time the light has taken to travel from the emitter to
an object of interest and back to the focal plane array.
[0030] The TOF sensor 108 can be implemented, for example, as an
integrated sensor chip. As shown in FIG. 1, the TOF sensor 108
includes active demodulation detection pixels 124, one or more
dedicated "spurious reflection detection" pixels 126 and one or
more reference pixels 128. Although the number and arrangement of
the demodulation detection pixels 124 can vary depending on the
implementation, in some implementations, the demodulation detection
pixels are in a 3.times.3 array. In some cases, the
spurious-reflection detection pixels may be referred to as smudge
detection pixels. Each spurious-reflection detection pixel 126 can
be implemented, for example, as a CCD pixel or a photodiode. The
demodulation detection pixels 124 provide the primary signals for
determining the proximity of an object outside the module. The
demodulation detection pixels 124 preferably are centered below the
light detection channel lens 120B. The center optical emission axis
of the emitter 106 preferably is aligned with the emitter channel
lens 120A. Signals sensed by the spurious-reflection detection
pixel(s) 126 can be used to correct for spurious reflections such
as from a smudge (i.e., a blurred or smeared mark such as a
fingerprint or dirt) 130 on the transmissive cover (e.g., a cover
glass) 132 of a host device (e.g., a smart phone or other handheld
computing device). In some implementations, signals sensed by the
spurious-reflection detection pixel(s) 126 can be used to correct
for spurious reflections resulting from other direct reflections
such as from the cover glass, from a filter, or from other
optical/non-optical components in the optoelectronic module or host
device. If such corrections are not performed, the TOF sensor may
produce a spurious output signal, which can compromise the accuracy
of the proximity data collected. A small amount of light from the
emitter 106 can be reflected, for example, by the lens 120A back
toward the reference pixel(s) 128. Signals from the reference
pixel(s) 128 can be used to compensate for thermal drift and/or to
provide a zero distance measurement.
[0031] The sensor's processing circuitry can be implemented, for
example, as one or more integrated circuits in one or more
semiconductor chips with appropriate digital logic and/or other
hardware components (e.g., read-out registers; amplifiers;
analog-to-digital converters; clock drivers; timing logic; signal
processing circuitry; and/or a microprocessor). The processing
circuitry may reside in the same semiconductor chip as the sensor
108 or in one or more other semiconductor chips.
[0032] In the example of FIG. 1, an interior wall 115 of the spacer
114 provides optical isolation between the module's two chambers
(i.e., the light emission channel 102 and the light detection
channel 104). The reference pixel(s) 128 are located in the emitter
chamber 102, whereas the demodulation detection pixels 124 and the
dedicated spurious-reflection detection pixel(s) 126 are located in
the detection chamber 104. The interior wall 115 prevents emitter
light, which is reflected, for example, back into the emission
chamber 102 by the lens 120A, from impinging on the demodulation
detection pixels 124.
[0033] In some of the examples described here, it is assumed that
spurious reflections may be caused by a smudge on the cover glass
of the host device. However, the modules and techniques described
below also can be applicable to spurious reflections resulting from
other direct reflections such as from the cover glass, from a
filter, or from other optical/non-optical components in the
optoelectronic module or host device.
[0034] Preferably, the spurious-reflection detection pixel(s) 126
should be positioned relative to the demodulation detection pixels
124 such that, in the absence of a smudge on cover 132 of the host
device, the spurious-reflection detection pixel 126 senses, at
most, a signal representing only a relatively low optical intensity
of light reflected by an object in a scene outside the module 100.
In contrast, when a smudge 130 is present on the surface of the
cover 132 of the host device, the smudge may redirect some of the
light reflected by the external object toward the
spurious-reflection detection pixel(s) 126 such that they sense a
significantly higher optical intensity. For example, the
spurious-reflection detection pixel 126 can be positioned on the
sensor 108 a sufficient lateral distance (d) from the demodulation
detection pixels 124 such that, in the absence of a smudge on cover
132 of the host device, the spurious-reflection detection pixel 126
senses, at most, only a relatively low optical intensity of light
reflected by an object in a scene outside the module 100. On the
other hand, a smudge 130 on the surface of the cover 132 of the
host device can cause some of the light reflected by the external
object to be redirected toward the spurious-reflection detection
pixel 126 such that it senses a significantly higher optical
intensity.
[0035] The optical intensity sensed by the spurious-reflection
detection pixel 126 can be used by the sensor's processing
circuitry to determine whether a smudge is present on the cover
glass 132 and to determine how much light (i.e., amplitude and
phase) collected by the active pixels 124 is due to the smudge
rather than the object of interest. For example, as illustrated by
FIG. 2, during each TOF frame, the sensor's control circuitry can
initiate an intensity (DC) measurement of the light sensed by the
spurious-reflection detection pixel 126 (block 200). Based at least
in part on the output of the spurious-reflection detection pixel,
the sensor's processing circuitry then can determine whether a
smudge is present on the cover glass 132 (block 202). In
particular, in some implementations, a high intensity sensed by the
spurious-reflection detection pixel 126 in combination with a TOF
sensor output of about zero (i.e., cover glass level) indicates the
presence of an object on the surface of the cover glass 132. On the
other hand, a high intensity sensed by the spurious-reflection
detection pixel 126 in combination with a TOF measurement greater
than zero indicates the presence of a smudge. Further, the
intensity sensed by the spurious-reflection detection pixel 126 is
proportional to the magnitude of the smudge vector. As the phase of
the smudge vector is available to the sensor's processing
circuitry, the processing circuitry can use vector subtraction to
compensate for the distance error caused by the smudge (block 204).
For example, the intensity of the light reflected by the smudge 130
can be measured by the spurious reflection pixel 126. Assuming that
the path length to the smudge 130 is known to the sensor's
processing circuitry, the phase also can be determined (e.g., as
part of a calibration process). If the magnitude of the light on
the spurious-reflection detection pixel 126 is known, the magnitude
of the light component incident on the active pixels 124 that is a
result of reflection from the smudge 130 can be inferred by the
sensor's processing circuitry. The phase of the light component
that is a result of the reflection from the smudge 130 can be
factored out of the measured signals obtained from the active
pixels 124.
[0036] In some implementations, as indicated by FIG. 3, the
optoelectronic module includes a reflector 140 to direct light
reflected by a smudge 130 toward the spurious-reflection detection
pixel(s) 126. The reflector 140 can be positioned, for example, in
the vicinity of the spurious-reflection detection pixel 126 just
below the transmissive cover 132 of the host device. The presence
of the reflector 140 can enhance sensing by the spurious-reflection
detection pixel 126 by controlling the specific reflection angles
at which reflected light is detected. Thus, in the absence of a
smudge 130, light 134 from the emitter 106 can reach an object 135
outside the module and can be reflected by the object 135 for
sensing by the demondulation detection pixels 124. The presence of
a smudge 130 can cause some of the emitter light 136 to be
reflected back into the module. The reflector 130 can re-direct
some of that reflected light toward the spurious-reflection
detection pixel 126. The sensor's processing circuitry can use the
change (i.e., increase) in intensity sensed by the
spurious-reflection detection pixel 126 to determine that there is
a smudge 130 on the transmissive cover 132 and/or to compensate for
a distance error caused by the smudge.
[0037] In some cases, emitter light reflected by a smudge 130 on
the transmissive cover 132 results in multiple internal reflections
142 off opposing inner surfaces 132A, 132B of the cover as shown in
FIG. 4. Such light 142 may be reflected, for example, by internal
reflection within the transmissive cover 132. Some of the reflected
light 142, however, will pass, for example, through the sensor-side
surface 132A of the cover 132. This light 144 can be directed to
the spurious-reflection detection pixel(s) 126 by a light guide 146
coupled between the surface 132A and the pixel 126. Thus, in the
absence of a smudge 130, light 134 from the emitter 106 can reach
an object 135 outside the module and can be reflected by the object
135 for sensing by the demondulation detection pixels 124. The
presence of a smudge 130 can cause some of the emitter light 136,
142 to be reflected back into the module. The light guide 146 can
guide such light 144 to the spurious-reflection detection pixel
126. The sensor's processing circuitry can use the change (i.e.,
increase) in intensity sensed by the spurious-reflection detection
pixel 126 to determine that there is a smudge 130 on the
transmissive cover 132 and/or to compensate for a distance error
caused by the smudge.
[0038] FIG. 5 illustrates another implementation of an
optoelectronic module that can facilitate enhanced detection of a
smudge 130, for example, on the cover glass 132 of the host device.
In this example, a smudge detection area 160 is defined on the
object-side (i.e., exterior) surface 162 of the cover glass 132.
The pre-specified smudge detection area 160 lies, for example, near
the edge of the field of illumination (FOI) of the light emitter
106 (e.g., a VCSEL), outside the field of view (FOV) of the TOF's
demodulation detection pixels 124. As further illustrated in FIG.
5, one or more light absorbing regions 164 are provided in or on
the material of the detection channel passive optical element 120B
so as to leave only a relatively narrow straight path 166 from the
smudge detection area 160 of the cover glass 132 to the
spurious-reflection detection pixel(s) 126. The light absorbing
regions are substantially non-transparent (i.e., opaque) to light
at a wavelength emitted by the light emitter Although the example
of FIG. 5 shows two such light absorbing regions 164, other
implementations may include only a single light absorbing region,
whereas some implementations may have more than two light absorbing
regions in the material of the detection channel passive optical
element 120B. If the light emitter 106 emits, for example, light in
the infra-red (IR) range, each light absorbing region 164 can be
formed as an IR-absorbing region, for example, by laser blackening
specified regions of the passive optical element 120B or by
depositing a thin coating of black chrome on the specified areas of
the passive optical element 120B.
[0039] FIG. 6 illustrates an optoelectronic module 200 that can
help block at least some light 170 reflected by a smudge 130 on the
cover glass 132 of the host device, or light 172 reflected by the
cover glass itself, and prevent the reflected light from impinging
on the demodulation detection pixels 124. The module 200 includes a
passive optical element (e.g., a lens) 120A that intersects the
optical emission path 174, and a passive optical element 120B
(e.g., a lens) that intersects the optical detection path 176. In
the illustrated example, both passive optical elements 120A, 120B
rest on the surface of a transparent substrate 178. In other
implementations, the passive optical elements 120A, 120B may be
part of an optics member as shown, for example, in FIG. 1.
[0040] As further illustrated in FIG. 6, the passive optical
element 120B for the detection channel includes one or more light
absorbing regions 180 that absorb light at the wavelength(s)
emitted by the emitter 106. In some instances, each light absorbing
region 180 is formed as an IR-absorbing region, for example, by
laser blackening specified regions of the passive optical element
120B or by depositing a thin coating of black chrome on specified
areas of the passive optical element 120B. The light absorbing
regions 180 can be positioned on the passive optical element 120B
so as to intersect, and effectively block, light 170 reflected by
the smudge and/or light 172 reflected by the cover glass 132 that
otherwise would impinge on the demodulation detection pixels 124.
On the other hand, the passive optical element 120B can direct some
parts 182 of the light reflected by the smudge 130 toward the
spurious-reflection detection pixels 126. Likewise, light reflected
by an object 135 in a scene outside the module 200 can be reflected
along paths (e.g., path 176) that pass through the passive optical
element 120B and impinge on the demodulation detection pixels
124.
[0041] FIG. 7 illustrates an optoelectronic module 202 that
includes one or more light redirecting elements 190 that can
redirect some of the light 192, 194 impinging on the detection
channel's passive optical element 120B toward the
spurious-reflection detection pixels 126 and away from the sensor
108 (i.e., away from the demodulation detection pixels 124). In
particular, as shown in FIG. 7, the surface of the optical element
120B for the detection channel can have one or more passive optical
elements 190, such as refractive or diffractive lenses, that
redirect the light 192, 194 toward the spurious-reflection
detection pixels 126. In some implementations, the passive optical
elements 190 are integrated within the optical element 120B. The
light redirecting elements 190 can be positioned on the passive
optical element 120B so as to intersect light 192 reflected by the
smudge and/or light 194 reflected by the cover glass 132 that
otherwise might impinge on the demodulation detection pixels 124.
On the other hand, light reflected by an object 135 in a scene
outside the module 200 can be reflected along paths (e.g., path
176) that pass through the passive optical element 120B and impinge
on the sensor's demodulation detection pixels 124.
[0042] FIG. 8 illustrates another optoelectronic module 204 in
which the emitter channel's passive optical element 120A has one or
more light redirecting elements 196 that can redirect some of the
emitter light 174 toward a particular region 133 on the outer
surface 132B of the cover glass 132. Each light redirecting element
196 can be, for example, a passive optical element such as a
refractive or diffractive element. In some implementations, the
light directing elements 190 are integrated within the optical
element 120B. If a smudge 130 is present on the surface 132B of the
cover glass 132, light 198 reflected by the smudge 130 at the
particular region 133 of the cover glass surface passes through the
passive optical element 120B, which directs the light 198 toward
the spurious-reflection detection pixels 126. Preferably, the
spurious-reflection detection pixel(s) 126 are located at a
sufficiently large lateral distance from the sensor 108 such that
the light incident on the spurious-reflection detection pixel(s)
126 is based only (or at least primarily) on light reflected by the
smudge 130 and not light reflected by the object 135. The detection
channel's passive optical element 120B should be designed to direct
the light 198 from the smudge 130 at the proper angle so that the
light 198 impinges on the spurious-reflection detection pixel(s)
126.
[0043] In some instances, one or more of the features described in
the foregoing examples may be combined in a single module. FIG. 9
illustrates one such example of a module 206 in which the emitter
channel optical element 122A includes a light directing element 196
as described in connection with FIG. 8 and the detection channel
optical element 122B includes a light absorbing region 180 as
described in connection with FIG. 7. Modules includes other
combinations of the various features described in this disclosure
can be provided to improve the modules' ability to distinguish
between signals indicative of reflections from an object interest
and signals indicative of a spurious reflections.
[0044] As described above, the modules can include one or more
dedicated spurious-reflection detection pixels 126 that are
separate from the demodulation detection pixels 124. As also
described, the modules also may include one or more dedicated
reference pixels 128 that can be used to compensate for thermal
drift/or and to provide a zero distance measurement (see, e.g.,
FIG. 1). In some implementations, however, the module can include
pixels that serve as combined reference and spurious-reflection
detection pixels. An example is illustrated in FIG. 10, which
includes one or more pixels 126A whose output can be used by the
sensor's processing circuitry to correct for spurious reflections
such as from a smudge and also to compensate for thermal drift/or
and to provide a zero distance measurement. For example, signals
from the pixels 126A can be used to determine both amplitude and
phase during calibration of the module. During subsequent
operation, changes in amplitude of the detected signals of the
pixels 126A can indicate the presence of the smudge and can be used
to correct for spurious reflections caused by the smudge. Likewise,
phase shifts in the detected signals of the pixels 126A can be used
to compensate for thermal drift.
[0045] In some implementations, instead of, or in addition to,
dedicated smudge pixels, signals obtained from the demodulation
detection pixels 124 can be used to determine the wave component
(i.e., amplitude, phase) that is caused by reflection from a smudge
130 on the surface of the cover glass 132. To do so, the wave
component caused by the smudge reflection can be estimated, for
example, by repeating measurements at two different modulation
frequencies. Assuming the distance between the smudge 130 and the
emitter 106 is known to the module's processing circuity (e.g.,
based on a previously stored value in memory and/or calibration of
the module), the additional wave component resulting from the
presence of the smudge 130 can be determined by the processing
circuity. Any such additional wave component would be common to
signals detected by the demodulation detection pixels 124 at both
modulation frequencies. The additional wave component caused by the
smudge 130 can be eliminated (i.e., subtracted out) through known
vector manipulation techniques, and the wave components resulting
from light reflected by the object of interest outside the module
can be calculated. The resulting phase shift then can be used to
calculate the distance to the object 135.
[0046] FIG. 11 is an example of a phasor diagram 300 illustrating
the various light components in which two different modulation
frequencies are used as described above. In FIG. 11, 302 is the
wave component (i.e., vector representing amplitude, phase) caused
by reflection from the smudge, 304 is the wave component caused by
light reflected from the object at the low modulation frequency,
306 is the wave component that represents the sum of the light
reflected both by the object and by the smudge at the low
modulation frequency, 308 is the wave component caused by light
reflected from the object at the high modulation frequency, and 310
is the wave component that represents the sum of the light
reflected both by the object and by the smudge at the high
modulation frequency. The wave components (i.e., phasors) 302, 304,
306, 308, and 310 in FIG. 11 are rotated by a phase corresponding
to the known distance of the smudge measured at the respective
modulation frequency. In the phasor diagram 300, the two phasors
306, 310 (representing the received light signal at low and high
demodulation frequencies, respectively) lie on a circle whose
center corresponds to the amplitude of the smudge component. Thus,
vector manipulation can be used to eliminate the wave component
caused by the smudge.
[0047] In some implementations, it can be advantageous to increase
the difference between the applied modulation frequencies. Further,
it some cases, the lower frequency can be replaced by two DC
measurements (i.e., switching the illumination on and off,
respectively).
[0048] As previously described, the foregoing modules and
techniques can be applicable to correction of errors caused by
spurious reflections resulting from reflections from the cover
glass, from a filter, or from other optical/non-optical components
in the optoelectronic module or host device.
[0049] The modules described here can be integrated advantageously
into devices such as smart phones, tablets, and other host devices
in which space is at a premium.
[0050] Various modifications can be made to the foregoing examples.
Further, features from the different examples can, in some
instances, be integrated in the same module. Other implementations
are within the scope of the claims.
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